1. Field of the Invention
The present invention relates to a small electronic component, an electronic circuit board, and a method of manufacturing a small electronic component.
2. Description of the Related Art
Various electronic components including a magnetic core and a winding coil have been proposed. As one type of such electronic components, there has also been proposed an electronic component further including, in addition to the magnetic core and the winding coil, a magnetic cover part configured to cover the magnetic core and the winding coil (Chinese Patent Application Publication No. 104051129, etc.). The magnetic cover part is formed by molding through use of a magnetic material formed of magnetic powder and a resin.
Meanwhile, the electronic component as disclosed in Chinese Patent Application Publication No. 104051129 is often used as an electronic component to be mounted on a wiring board, and an electronic circuit board including the electronic component is widely used in application to vehicle installation, application to small electronic equipment, such as a mobile phone and a smartphone, and other consumer applications. Therefore, the electronic component for surface mounting to be mounted on a wiring board is required to have at least one kind of characteristics selected from at least characteristics (1) to (7) listed below, in accordance with a manufacturing process of an electronic circuit board including the electronic component, intended use and application thereof, and a size and a mounting density thereof. The electronic component may be required to have a plurality of kinds of the characteristics or may be required to have all kinds of the characteristics simultaneously.
(1) Magnetic powder is less liable to escape from the surface of a magnetic cover part (magnetic powder escape prevention ability).
(2) The bonding between a wiring board and an external electrode of the electronic component is excellent (external electrode bonding property).
(3) The degradation and trouble of the electronic component caused by insulation breakdown due to static electricity can be suppressed (withstand voltage characteristics)
(4) The occurrence of rust under a high-temperature and high-humidity environment can be prevented (antirust ability).
(5) The magnetic characteristics of the magnetic cover part are not significantly changed by heating at a time of surface mounting (heat resistance).
(6) The magnetic cover part after being thermally cured is excellent in mechanical strength (strength after heat curing).
(7) Further, the electronic component used in application to surface mounting is required to have a small size and have a complicated structure and shape in some cases in order to be adaptable to an increase in mounting density and downsizing of the electronic circuit board. In such case, in manufacturing of the electronic component, that is, molding, a filling failure of a magnetic material is liable to occur. Thus, in manufacturing of the electronic component, it is also desired that molding be easy (moldability).
Meanwhile, the electronic component for surface mounting is a general-purpose component and is widely used in various intended uses and applications, e.g., application to installation in vehicles such as an automobile and a railroad vehicle, application to mobile terminals such as a smartphone, a tablet terminal, and a mobile phone, application to wearable terminals such as a wristwatch-type terminal and an eyeglass-type terminal, application to personal computers such as a desktop personal computer and a notebook personal computer, application to audio-video equipment such as a liquid crystal display, an organic EL display, and audio equipment, and application to a digital camera. Therefore, it is important that the electronic component for surface mounting satisfy the characteristics that are highly demanded on the market, that is, all the characteristics (1) to (7) described above so as to widely meet various needs of users irrespective of whether the characteristics are actually required by individual users that use the electronic component.